HSAB Principle Applied to the Time Evolution of Chemical Reactions

Abstract

Time evolution of various reactivity parameters such as electronegativity, hardness, and polarizability associated with a collision process between a proton and an X- atom/ion (X = He, Li(+), Be(2+), B(3+), C(4+)) in its ground ((1)S) and excited((1)P,(1)D,(1)F) electronic states as well as various complexions of a two-state ensemble is studied using time-dependent and excited-state density functional theory. This collision process may be considered to be a model mimicking the actual chemical reaction between an X-atom/ion and a proton to give rise to an XH(+) molecule. A favorable dynamical process is characterized by maximum hardness and minimum polarizability values according to the dynamical variants of the principles of maximum hardness and minimum polarizability. An electronic excitation or an increase in the excited-state contribution in a two-state ensemble makes the system softer and more polarizable, and the proton, being a hard acid, gradually prefers less to interact with X as has been discerned through the drop in maximum hardness value and the increase in the minimum polarizability value when the actual chemical process occurs. Among the noble gas elements, Xe is the most reactive. During the reaction: H(2) + H(+) --> H(3)(+) hardness maximizes and polarizability minimizes and H(2) is more reactive in its excited state. Regioselectivity of proton attack in the O-site of CO is clearly delineated wherein HOC(+) may eventually rearrange itself to go to the thermodynamically more stable HCO(+).

Crystal Structure and DFT Studies of 4-(1-Benzyl-5-Methyl-1h-1,2,3-Triazol-4-Yl)-6-(3- Methoxyphenyl)pyrimidin-2-Amine

“…Physically, μ describes the escaping tendency of electrons from an equilibrium system 39 . The value of μ for title compound is presented in table 5 (row 5).…”

Density dynamics in some quantum systems

“…Hence, the validity of the HSAB principle is provided [166] in a dynamical context as the maximum g value decreases and the minimum a value increases in the order 1 S Figures 19 and 20, respectively, show the time evolution of hardness and polarizability of noble gas systems namely, He, Ne, Ar, Kr, Xe during protonation. As expected, the hardness and polarizability attain, respectively, the maximum and the minimum in the encounter region.…”

“…There is no general excited-state DFT except for systems involving states of lowest energy for a given symmetry class [1,2,160] and two-state and multistate ensembles. [161][162][163][164][165] Time evolution of various reactivity parameters during ion-atom [34,166,167] and ion-molecule [168] processes have been studied in detail by our group. Hardness (g) [169,170] for an N electron system with energy E can be defined as,…”

Synthesis, Crystal Structure, DFT and Antibacterial Activity Studies of (E)-2-Benzyl-3-(Furan-3-Yl)-6,7-Dimethoxy-4-(2-Phenyl-1h-Inden-1-Ylidene)-1,2,3,4-Tetrahydroisoquinoline

“…Physically, μ describes the escaping tendency of electrons from an equilibrium system 32 . The value of μ for the title compound is presented in Table 4 (row 5).…”